Elucidation of Hot-Electron Transport and Exploitation of Hot-Carrier Plasmonics via Nonlinear Optical Effects

高能电子的行为被称为“热”电子，在化学合成、能量收集和信息技术中的应用是必不可少的。这一研究领域的进一步进展需要加深对这种带电电子在用光激发后的行为的了解。这种激发过程是一个复杂的现象，由许多连续的过程组成，其中大多数过程发生在十亿分之一秒内。这个研究小组利用其他光学效应控制这些热电子的行为，以了解电子的产生、传输和衰变。此外，利用光诱导热电子的超快行为对光进行全光控制。通过这个项目获得的知识为半导体和光学的接口奠定了基础，并导致了对光检测和处理设备的设计和实施的新见解。这项研究，包括高中和大学教育，促进了未来科学家和工程师的多学科思维。该项目广泛传播从这项研究工作中获得的跨学科知识，通过研究和教育的整合鼓励青年的早期参与，并增加来自少数群体的高中生的学习机会。等离子体诱导的热载流子的动力学对广泛的光物理和光化学过程至关重要。目前的理解在一定程度上受制于主流表征方法的能力。此外，热载流子等离子体的基本原理和应用主要集中在线性光学区域，而研究热载流子参与非线性光-物质相互作用的工作相当有限。该项目旨在通过非线性光学手段阐明热载流子的产生、传输和热化的动力学，并进一步利用热载流子诱导的非线性光学过程来检测和处理光子和量子系统中的信号。本研究的总体内容是建立一种基于二阶和三阶非线性光学效应的热载流子超快动力学研究和利用的新技术。这种新的非线性过程被探索在杂化等离子体平台上，其中纳米结构的金属与接受电子的材料连接。特别值得关注的是实现了两种热载流子诱导现象，即瞬时光学克尔非线性和瞬时二次谐波产生，用于研究热电子动力学和实现超快全光控制光。这项研究的成功实施带来了对降维的光-物质相互作用的新理解，并促进了对热载流子物理、光信号处理和量子传输的更好理解。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The behavior of energetic electrons, termed “hot” electrons, is essential for applications in chemical synthesis, energy harvesting, and information technology. Further advances of this area of research demand deepened knowledge of the behavior of such charged electrons after excitation with light. This excitation process is a complicated phenomenon consisting of a number of sequential processes, most of which happen within one billionth of a second. This research team controls the behavior of these hot electrons with other optical effects to understand the generation, transport, and decay of electrons. Moreover, the ultrafast behavior of optically induced hot electrons is harnessed for the all-optical control of light. The knowledge gained through this project lays the groundwork at the interface of semiconductors and optics, and leads to new insights into the design and implementation of devices for the detection and processing of light. This research, included with high school and collegiate education, promotes multidisciplinary thinking of the up-and-coming scientists and engineers. The project broadly disseminates interdisciplinary knowledge derived from this research effort, encourages early engagement of the youth via integration of research and education, and enhances the learning opportunities for high school students from minority groups.The dynamics of plasmonically induced hot carriers is pivotal to a wide range of photophysical and photochemical processes. The current understanding is partially constrained by the capacities of prevailing characterization methods. Moreover, the fundamentals and applications of hot-carrier plasmonics are predominantly focused on the linear optical regime, while rather limited work has investigated the involvement of hot carriers in nonlinear light-matter interactions. This project aims to elucidate the dynamics of the generation, transfer, and thermalization of hot carriers via nonlinear optical means, and furthermore, to exploit hot-carrier induced nonlinear optical processes for signal detection and processing in photonic and quantum systems. The overall content of this research is to establish a new technique for the investigation and utilization of the ultrafast dynamics of hot carriers based on the second- and third-order nonlinear optical effects. Such novel nonlinear processes are explored in hybrid plasmonic platforms, where nanostructured metals interface electron-accepting materials. Of particular interest are the implementations of two hot-carrier induced phenomena, namely, the transient optical Kerr nonlinearity and the transient second-harmonic generation, for the investigation of hot-electron dynamics and the realization of ultrafast all-optical control of light. The successful execution of the research leads to new understanding of light-matter interactions at reduced dimensions, and facilitates improved understanding of hot-carrier physics, optical signal processing, and quantum transport.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.